We propose research on the mechanisms by which the transcription of nucleic acids is regulated. Our goal is to understand the molecular (biochemical and structural) mechanisms by which genes are turned on and off. Our studies deal primarily with bacteria and bacterial viruses where a powerful genetics is at hand. We shall sequence the lactose operator and identify the DNA sequence with which the lactose repressor interacts. We shall also study the structure of the lactose repressor in the hope of understanding the protein-nucleic acid interactions. We shall also sequence the rest of the control region for the lactose operon (the promoter and the CAP binding site). We plan to study factors that influence the specificity of the RNA polymerase or that act as positive control elements (specifically the Q-gene product of phage gamma, responsible for late messenger synthesis, and the C-protein of the arabinose operon, a specific positive regulator). We shall pursue studies on the synthesis of ribosomal RNA and the replication of the RNA phage Q beta, with the aim of elucidating the regulatory roles of the host factors involved in the replication process.